How do Rotary Screw Air Compressors Work Diagram?

Firstly, let’s see the HD animation of the working principle of German GEA screw compressor, it’s so cool! Let’s start with a few moving pictures to get a feel for it:

Rotary Screw Air Compressor History

■ In 1934 Lysholm (Riesmann), a professor at the Royal Swedish Academy of Engineering, invented the first twin-screw gas compressor.

■ From the 1960s, oil-injected twin-screw units are used in refrigeration units. Sweden SRM (twin screw) first invented bilateral asymmetric profile screw, so that the efficiency of the screw machine greatly improved.

■ 1960 French Zimmern (Xin Maien) (single screw) invented a new structure of the single screw. 1962 trial production of the first prototype.

■ In the early 70s, the Netherlands GRASSO (GRASSO) made the first single-screw refrigeration compressor.

■ 1972, Japan began production of single-screw air compressors.

■ 1982, began production of single screw refrigeration compressor.

Screw compressor cylinder is equipped with a pair of intermeshing spiral yin and yang rotor, the two rotors have a few concave teeth, the two rotate against each other. Between the rotor and the casing and rotor clearance is only 5 to 10 silk, the main rotor (also known as the yang rotor or convex rotor), by the engine or motor drive (most of the motor drive), the other rotor (also known as the yin rotor or concave rotor) by the main rotor through the formation of the oil film formed by the injection of oil to drive, or by the main rotor end and the concave rotor end of the synchro-gear drive.

So there is no metal contact in the drive (theoretically). The length and diameter of the rotor determine the compressor discharge volume (flow rate) and discharge pressure; the longer the rotor, the higher the pressure; the larger the rotor diameter, the higher the flow rate.

The spiral rotor groove is filled with gas as it passes through the suction port. When the rotor rotates, the rotor groove is closed by the wall of the casing, forming a compression chamber, when the rotor groove is closed, the lubricating oil is sprayed into the compression chamber to seal.

Cooling and lubrication. When the rotor rotates and compresses the lubricant + gas (referred to as oil-gas mixture), the volume of the compression chamber decreases and the oil-gas mixture is compressed towards the exhaust port. When the compression chamber through the exhaust port, the oil and gas mixture from the compressor discharge, complete a suction – compression – exhaust process.

Each rotor of a screw machine is supported by a friction-reducing bearing, which is held in place by an end cap near the end of the rotor shaft. The inlet end is supported by roller bearings, and the exhaust end is supported by a pair of conical roller bearings usually on the exhaust end of the bearings so that the rotor positioning, that is, thrust bearings, resistance to axial thrust, to withstand radial loads, and to provide the necessary axial operation of the minimum clearance.

The operating cycle can be divided into three processes: suction, compression and exhaust. As the rotor rotates, each pair of intermeshing teeth successively complete the same work cycle.

Rotary Screw Compressor Advantages

1) High reliability. Screw compressor parts less, no wearing parts, so it runs reliably, long life, overhaul intervals of up to 4-8 millionh.

2) Easy to operate and maintain.

3) Good power balance. Especially suitable for use as a mobile compressor, small size, light weight, covers an area of less.

4) Strong adaptability. Screw compressor has the characteristics of forced gas transmission, volumetric flow is almost independent of the exhaust pressure, in a wide range to maintain high efficiency, in the compressor structure does not make any changes in the case of a wide range of work materials.

5) Multi-phase mixed transport. Screw compressor rotor teeth actually leave a gap between the surface, and thus can withstand the impact of liquid, can be transported containing liquid gases, dust-containing gases, easy to polymerisation of gases and so on.

Rotary Screw Compressor Disadvantages

(1) high cost. Because the rotor tooth surface of the screw compressor is a space surface, need to use special tools in the expensive special equipment for processing. In addition, the screw compressor cylinder machining accuracy also has high requirements.

(2) can not be used for high-pressure occasions. Due to the rotor stiffness and bearing life and other aspects of the limitations, screw compressor can only be used for medium and low pressure range, exhaust pressure is generally not more than 3MPa.

(3) can not be used for miniature occasions. Screw compressors rely on gap sealing gas, generally only volume flow greater than 0.2m/min, screw compressors have superior performance.

Adjustment of displacement:

Variable speed adjustment, screw compressor displacement and the number of revolutions is proportional to the relationship. Therefore, change the number of compressor speed can achieve the purpose of regulating the exhaust volume.

Stopping regulation:

The use of compressor stopping to adjust the amount of exhaust, there are two common forms:

For air compressors greater than 5kW this is the most commonly used method, with a wide range of regulation and low losses, in effect it is a combination of on/off regulation with various unloading systems.

The length of the idling cycle can be based on the number of starts and stops the motor can withstand without overheating, and the economy during operation. The latter because the system can decide to stop, or continue idling, depending on the direction of air consumption.

Controlled intake regulation:

The use of the compressor suction pipe on the inlet valve to regulate. Controlled intake regulation is divided into two kinds of stopping intake and throttling intake.

Inlet and outlet pipe connection regulation:

From the structure of the device, this method of regulation is simple, it only needs to be installed in the discharge pipeline a regulating valve. When regulating the working condition, the compressed gas flows back to the suction port along the bypass pipe through this regulating valve.

Idle regulation:

It is actually stopping the suction and inlet and exhaust pipe connectivity regulation jointly used a comprehensive regulation method, using a cut-off in the suction at the same time, can make the inlet and exhaust pipe connectivity of the load reduction valve. Idle regulation of the diagram shown in Figure 4-49. It can be stopped on the basis of suction regulation diagram, taking into account the gas to the intake pipeline (atmosphere) discharge (installed in the compressor discharge check valve before the connecting pipe) and get.

Slide valve adjustment:

Slide valve is a traditional compressor regulation, by adjusting the position of the slide valve to change the compressor’s discharge volume.

Usually used in small air compressors, such as automotive air conditioning compressors, household air conditioning compressors, refrigerator compressors and so on. For large compressors, often use electronic control, frequency conversion speed control and other higher precision regulation to meet the requirements.